Yue Leng, of the University of Cambridge in the United Kingdom, and colleagues followed 9,692 people participating in a European study, tracking their sleep patterns and any incidence of stroke for nearly 10 years. The men and women, average age 62 when the study started, reported their sleep duration once between 1998 and 2000, and again four years later. They told how many hours they slept a night and how well they slept.
Over the follow-up period, 346 people had strokes. Those who slept longer than eight hours had a 46% increased stroke risk, and those who slept less than six hours had an 18% higher risk. But the number in the group reporting less than six hours of sleep a night was too small to call that link statistically solid, Leng told HealthDay. Those who reported being long sleepers in both of the two surveys faced double the risk of stroke when compared to those who reported average sleep times. And people whose sleep pattern changed – from sleeping less than six hours a night to more than eight hours a night – had about four times the risk of stroke as those who consistently got an average amount of sleep, Leng found.
Lack of sleep can lead to higher stress hormone levels, in turn raising blood pressure and stroke risk. But after Leng took factors such as high blood pressure into account, the relationship between long sleep and stroke risk persisted.